(Objective-C) MX Lookup Mail Server Domain by Email Address

How to find the mail server for a given email address. Returns the domain name of the primary mail server.

Note: This example requires Chilkat v11.0.0 or greater.

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#import <CkoDns.h>
#import <CkoJsonObject.h>
#import <NSString.h>

BOOL success = NO;

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

CkoDns *dns = [[CkoDns alloc] init];
CkoJsonObject *json = [[CkoJsonObject alloc] init];

NSString *emailAddr = @"bob@example.com";

// This gets all MX domains for an email address.  (Typically one domain.)
// The preferred domain will be at index 0 (see below).
success = [dns Query: @"MX" domain: emailAddr answer: json];
if (success == NO) {
    NSLog(@"%@",dns.LastErrorText);
    return;
}

int i = 0;
int count_i = [[json SizeOfArray: @"answer.mx"] intValue];
while (i < count_i) {
    json.I = [NSNumber numberWithInt: i];
    NSString *domain = [json StringOf: @"answer.mx[i].domain"];
    NSLog(@"%@",domain);
    i = i + 1;
}